The invention relates to a vision aid with an autofocussing means, with a means for changing the focal length and with a means for matching the parallax between the tubes of the vision aid to the respectively set focal length.
One such vision aid (telescopic spectacles) with an autofocussing means, with a means for changing the focal length and with a means for matching the parallax between the tubes of the vision aid to the respectively set focal length, is disclosed in WO 96/09566 A (or the essentially identical U.S. Pat. No. 5,971,540 A). The known vision aid is intended for use as telescopic spectacles.
The known telescopic spectacles have an automatic and/or manual focussing means, a device for manually changing the magnification factor, and a device for automatic, mechanical parallax compensation corresponding to the respective focal length. If for example during vascular surgery, as a result of the location of the various surgical sites, a change of the working distance is necessary, the focal length and the parallax angle are automatically or manually adapted to the new working distance. This ensures optimum adjustment of the vision aid corresponding to the surgery. In addition, the user of the vision aid can assume the ergonomic position which is most advantageous at the time so that it is possible to operate without fatigue. In addition, the known vision aid makes it possible to adapt the magnification factor at each chosen working distance to the respective requirement. The known vision aid which is worn using a headset allows the user to largely freely choose the working distance and the magnification factor used. The control device is a foot-operated switch. In order not to lose the 3-D image when the working distance and the sharpness setting change, the known vision aid uses an autofocussing means which, by mechanically changing the angle of the tubes of the vision aid to one another, matches the parallax angle to the respective focal length. This type of matching of the parallax to the focal length which has been set at the time entails many defects.
(1) The tubes are mechanically adjusted by motors via gearing; this means a relatively great weight and thus little wearing comfort for the user.
(2) Since the tubes of the vision aid must be made movable to one another according to the lengthwise axis, the resistivity of the system to mechanical stress suffers.
(3) Each time the working distance changes, the parallax compensation means changes the position of the tubes to one another and thus also the angle of the eyepiece planes to the eyes of the user. This can lead to disruptive reflections and to a reduction in the size of the entry pupil and thus of the visual field.
(4) In practice it is hardly possible to produce systems which are independent of the user with this type of parallax compensation, i.e. each system is tailored to a certain user and his distal pupil distance. This necessitates higher investments if for example hospitals want to ensure than all surgeries can be carried out with autofocussing telescopic spectacles.
(5) If correction glasses which project over the eyepieces are attached to the latter, these glasses can touch the face of the user under certain circumstances when the position of the tubes change and thus distract him.
Furthermore, it would often be of great benefit to the user, for example in surgery, to be able to look at additional information such as the vital signs of the patients from the monitoring system, measurement scales or also x-ray, computerized tomography or other data during use of one such vision aid. The currently known telescopic spectacles do not offer this possibility.
Similar telescopic spectacles are known from AT E 98782 B.
U.S. Pat. No. 5,078,469 A discloses telescopic spectacles to which a video camera and a display unit are connected in order to take pictures of the surgical field.
WO 95/25979 A discloses a surgical microscope which has means for producing and displaying the three-dimensional video data of the surgical field and for reflecting in additional information, such as patient data.
U.S. Pat. No. 4,621,283 A describes a device to be worn on the head of a surgeon with telescopic spectacles and a photographic camera and a light source, the camera and the light source, regardless of the circumstance that they are worn on the top of the head at a distance, having a viewing direction which is essentially parallel to the viewing directions through the telescopic spectacles in front of the eyes of the surgeon, so that the image field viewed by the surgeon can be transmitted essentially from the same viewing angle via the recording means to a display screen.